Herbicidal tetrazolinones

ABSTRACT

Novel herbicidal tetrazolinones of the formula ##STR1## wherein Y is hydrogen, bromine or methyl, 
     R 1  is ethyl or n-propyl, and 
     R 2  is cyclopentyl or cyclohexyl, with the proviso that the total number of carbon atoms in R 1  and R 2  is 7 or 8. 
     The new tetrazolinones may be mixed with other herbicides.

The present invention relates to novel tetrazolinones, to a process for their preparation, and to their use as herbicides, especially as paddy-herbicides.

It has already been disclosed that tetrazolinone derivatives have herbicidal properties (see U.S. Pat. Nos. 4,618,365; 4,826,529; 4,830,661; 4,956,469; 5,003,075; 5,019,152 and 5,136,868 or the corresponding European Applications EP-A-146,279 and EP-A-202,929; further see EP-A-571,854, EP-A-571,855, EP-A-572,855 and EP-A-578,090).

There have now been found novel tetrazolinones of the formula (I) ##STR2## wherein Y is hydrogen, bromine or methyl,

R¹ is ethyl or n-propyl, and

R² is cyclopentyl or cyclohexyl,

with the proviso that the total number of carbon atoms in R¹ and R² is 7 or 8.

The compounds of the formula (I) can be obtained by a process in which compounds of the formula (II) ##STR3## wherein Y has the same meaning as mentioned above,

are reacted with compounds of the formula (III) ##STR4## wherein R¹ and R² have the same meanings as mentioned above, and

Hal is a leaving group such as chlorine, bromine, or the like,

in the presence of an inert solvent and, if appropriate, in the presence of an acid binder.

The novel tetrazolinones (I) exhibit powerful herbicidal properties, in particular against paddy-field weeds.

Suprisingly, the instant compounds of the formula (I) exhibit a substantially much greater herbicidal action against paddy-weeds than those compounds specifically shown in the references cited hereinabove.

Among the compounds of the formula (I), according to the invention, preferred compounds are those in which

Y is hydrogen or methyl.

Specifically, the following compounds, in addition to the compounds mentioned in the examples hereinbelow are of interest:

1-(2-bromophenyl )-4-(N-cyclopentyl-N-ethylcarbamoyl) -5(4H)-tetrazolinone,

1-(2-bromophenyl )-4-(N-cyclopentyl-N-n-propylcarbamoyl) -5(4H)-tetrazolinone,

1-(2-bromophenyl)-4-(N-cyclohexyl-N-ethylcarbamoyl) -5(4H)-tetrazolinone,

1-(2-bromo-6-methylphenyl)-4-(N-cyclopentyl-N-propylcarbamoyl) -5(4H)-tetrazolinone, and

1-(2-bromo-6-methylphenyl)-4-(N-cyclohexyl-N-ethylcarbamoyl) -5(4H)-tetrazolinone.

If use is made, in the above-mentioned process, of 1-(2-bromophenyl)-5(4H)-tetrazolinone and N-cyclohexyl-N-ethylcarbamoyl chloride, as the starting materials for example, the reaction can be expressed by the following reaction equation: ##STR5## The starting compounds of the formula (II) can be prepared in the manner similar to that described in "The Journal of Organic Chemistry", Vol. 45, No. 21, 1980, pages 5130-5136 or "The Journal of American Chemical Society", Vol. 81, No. 7, 1980, pages 3076-3079 .

As examples of compounds of formula (II), there may be mentioned the following:

1-(2-bromophenyl)-5(4H)-tetrazolinone,

1-(2-bromo-6-methylphenyl)-5(4H)-tetrazolinones, and

1-(2,6-dibromophenyl)-5(4H)-tetrazolinone.

The compounds of the formula (III) are well known in the field or organic chemistry. As specific examples thereof, there may be mentioned:

N-cyclopentyl-N-ethylcarbamoyl chloride,

N-cyclopentyl-N-n-propylcarbamoyl chloride, and

N-cyclohexyl-N-ethylcarbamoyl chloride.

In carrying out the process mentioned above, use may be made, as suitable diluents, of any inert organic solvents.

Examples of such diluents are aliphatic, cycloaliphatic and aromatic, optionally chlorinated, hydrocarbons such as pentane, hexane, cyclohexane, petroleum ether, ligroin, benzene, toluene, xylene, dichlormethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, chlorobenzene, dichlorobenzene, and the like; ethers such as diethyl ether, methyl ethyl ether, diisopropyl ether, dibutyl ether, dioxane, dimethoxyethane (DME), tetrahydrofuran (THF), diethylene glycol dimethyl ether (DGM), and the like; nitriles such as acetonitrile, propionitrile, and the like; acid amides such as dimethyl formamide (DMF), dimethyl acetamide (DMA), N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphoric triamide (HMPA), and the like; sulfones and sulfoxides such as dimethyl sulfoxide (DMSO), sulfolane, and the like; and bases such as pyridine.

The above-mentioned process may be carried out in the presence of acid binder, and as acid binders there may be mentioned, for example, inorganic bases including hydroxides, carbonates, bicarbonates, alcoholates, and hydrides of alkali metals, such as sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium methoxide, potassium methoxide, potassium tert-butoxide, lithium hydride, sodium hydride, potassium hydride, and the like; inorganic amides of alkali metals such as lithium amide, sodium amide, potassium amide, and the like; and organic bases including tertiary amines, dialkylaminoanilines and pyridines, such as triethylamine, 1,1,4,4-tetramethylethylenediamine (TMEDA), N,N-dimethylaniline, N,N-diethylaniline, pyridine, 4-dimethylaminopyridine (DMAP), 1,4-diazabicyclo[2,2,2]octane (DABCO), 1,8-diazabicyclo[5,4,0]-undec-7-ene (DBU), and the like. Furthermore, use may be made of organic lithium compounds such as, for example, methyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, phenyl lithium, dimethyl copper lithium, lithium diisopropyl amide, lithium cyclohexylisopropyl amide, lithium dicyclohexyl amide, n-butyl lithium·DABCO, n-butyl lithium·DBU, n-butyl lithium·TMEDA, and the like.

In the above-mentioned process the reaction temperature can be varied within a substantially wide range. In general, the reaction is carried out at a temperature of from about -30° C. to about 200° C., preferably from about -20° C. to about 130° C.

Further, the reaction is preferably carried out under normal pressure, although it is also possible to employ a higher or reduced pressure.

When the above-mentioned process is carried out, use may be made, for example, of 1.0 to 1.2 mols of the compound of the formula (III) in a diluent such as acetonitrile, for example, per mol of the compound of the formula (II) in the presence of 1 to 1.2 mols of an acid binder to obtain the desired compound.

The compounds represented by the general formula (I) according to the present invention can be used as herbicides for controlling paddy weeds.

Further, it has been discovered that a specially high herbicidal activity can be exhibited by herbicidal mixed compositions, comprising, as active components, the compounds represented by the general formula (I) according to the present invention, together with at least one of the members selected from the group consisting of herbicidally active sulfonamides, herbicidally active pyrazoles, herbicidally active propionanilides, herbicidally active triazines, herbicidally active carbamates, herbicidally active diphenylethers, herbioidally active pyrimidines and herbicidally active acid amides.

Surprisingly, the herbicidally mixed compositions according to the present invention have been found to exhibit herbicidal effects substantially higher than the sum of the herbicidal effects that can be exhibited individually by the herbicidally active, respective components and, as a result, the concentration of each of the active compounds can be substantially reduced when practicing weed control operations, while at the same time, a wide herbicidal spectrum can be obtained. Further, the herbicidal compositions according to the present invention have been found to expand the period of possible application, for example, in paddy rice cultivation, and exhibit excellent herbicidal effects for a period of from early stage of weed-emergence to weed-growing stage, with prolonged duration of activity and excellent residual effect, as well as phytotoxicity-free, excellent herbicidal effects on rice-plants.

As specific examples of the herbicidal sulfonamides to be employed in the present herbicidal mixed compositions there may be mentioned for example,

N-2-biphenylylsulfonyl N'-(4,6-dimethoxy-1,3,5-triazin-2yl -urea,

ethyl 5-[3-(4,6-dimethoxypyrimidin-2-yl)ureidosulfonyl]-1-methylpyrazole-4-carboxylate,

methyl 2-[3-(4,6-dimethoxypyrimidin-2-yl)ureidosulfonylmethyl]-benzoate,

3-(4,6-dimethoxy--1,3,5-triazin-2-yl)-1-[2-(2-methoxyethoxy)-phenylsulphonyl]urea,

N-(2-chloroimidazolo[1,2-a]pyridin-3-yl-sulfonyl)-N'-(4,6-dimethoxy-pyrimidin-2-yl) urea,

N'-(4,6-dimethoxypyrimidin-2-yl)-N"-(4-methylphenylsulfonylamino) -N"'-(4-ethoxycarbonyl-1-methylpyrazol-5-yl-sulfonyl)-guanidine, and

N-(2-cyclopropylcarbonylphenylsulfamoyl)-N'-(4,6-dimethoxypyrimidin-2-yl)-urea.

The above-mentioned compounds are also well known in the art (see Japanese Patent Publication No. 481/1984, Japanese Patent Laid-open Nos. 112379/1982, 56452/1982, 122488/1984, 38091/1989 and 70475/1989).

As specific examples of the herbicidally active pyrazoles to be employed in the present invention there may be mentioned, for example,

4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yl-P-toluenesulfonate,

2-[4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yl]acetophenone, and

2-[4-(2,4-dichloro-m-tolyl)-1,3-dimethylpyrazol-5-yloxy]-4-methylacetophenone.

As specific examples of the propionanilides to be employed in the present invention there may be mentioned, for example,

2-(β-naphthyloxy) propionanilide, and

(RS)-2-(2,4-dichloro-m-tolyloxy) propionanilide.

As specific examples of the herbicidally active triazines to be employed in the present invention there may be mentioned, for example,

2,4-bis (ethylamino)-6-(methylamino)-1,3,5-triazine, and

2-ethylamino-4-(1,2-dimethylpropylamino)-6-methylthio-1,3,5-triazine.

As specific examples of the herbicidally active carbamates there may be mentioned, for example,

S-p-chlorobenzyl diethylthiocarbamate,

S-1-methyl-1-phenylethyl piperidine-1-carbothioate, and

S-benzyl 1,2-dimethylpropyl(ethyl) thiocarbamate.

As specific examples of the herbicidally active diphenylethers to be employed in the present invention there may be mentioned, for example,

2,4,6-trichlorophenyl-4'-nitrophenylether, and

2,4-dichlorophenyl-3'-methoxy-4'-nitrophenylether.

As specific example of the herbicidally active pyrimidines to be employed in the present invention there may be mentioned, for example,

methyl 2-[(4,6-dimethoxy-2-pyrimidinyl)oxy]-6-[1-(methoxyimino) -ethyl]-benzoate.

As specific example of the herbicidally active acid amides to be employed in the present invention there may be mentioned, for example, (RS)-2-bromo-N-(α,α-dimethylbenzyl) -3,3-dimethylbutylamide.

The above-mentioned active compounds are known to be herbicidally active and are disclosed in "Pesticide Manual", 1991 published by The British Crop Protect Council.

A example of herbicidally active pyrimidines is one known compound that is described ion BCPC Weeds 1993, Brighton, Nov. 22-25th, 1993, Vol. 1., Ref. 2-b.

In the herbicidal mixed compositions according to the present invention, the mixing weight ratio of the active components may be varied over a relatively wide range.

In general, use may be made, per part by weight of the compounds represented by the general formula (I), of the herbicidal sulfonamides in from 0.01 to 2 parts by weight, preferably from 0.05 to 1 part by weight; the herbicidally active pyrazoles from 2.5 to 35 parts by weight, preferably from 3 to 15 parts by weight; the herbicidally active propionanilides in from0.6 to 50 parts by weight, preferably from 2.0 to 28 parts by weight; the herbicidally active triazines in from 0.06 to 10 parts by weight, preferably from 0.15 to 6 parts by weight; the herbicidally active carbamates in from 3 to 15 parts by weight, preferably from 5 to 10 parts by weight; the herbicidally active diphenylethers in from 5 to 35 parts by weight, preferably from 7 to 15 parts by weight; the herbicidally active pyrimidines in from 0.01 to 2 parts by weight, preferably from 0.1 to 1 part by weight; and the herbicidally active acid amides in from 3.5 to 25 parts by weight, preferably from 4.0 to 10 parts by weight, respectively.

The mixed compositions according to the present invention exhibit a strong herbicidal activity. Therefore the above-mentioned compositions may be used as herbicidal compositions and they may be advantageously used particularly as selective herbicidal compositions for paddy rice.

The herbicidal agents and mixed compositions according to the present invention can be applied, for example, to the following paddy weeds:

Dicotyledons of the following-genera: Polygonum, Rorippa, Rotala, Lindernia, Bidens, Dopatrium, Eclipta, Elatine, Gratiola, Lindernia, Ludwigia, Oenanthe, Ranunculus, Deinostema.

Monocotyledons of the following genera: Echinochloa, Panicum, Poa, Cyperus, Monochoria, Fimbristylis, Sagittaria, Eleocharis, Scirpus, Alisma, Aneilema, Blyxa, Eriocaulon, Potamogeton.

The herbicidal agents and mixed compositions according to the present invention can be applied specifically, for example, to the following paddy weeds in paddy fields:

    ______________________________________                                         Botanical names Latin names                                                    ______________________________________                                         Dicotyledons                                                                   Rotala indica   Rotala indica Koehne                                           False pimpernel Lindernia Procumbens Philcox                                   False loosestrife                                                                              Ludwigia prostrata Roxburgh                                    Largeleaf ponweed                                                                              Potamogeton distinctus A. Benn                                 American waterwort                                                                             Elatine triandra Schk.                                         Dropwort        Oenanthe javanica                                              Monocotyledons                                                                 Barnyard grass  Echinochloa oryzicola vasing                                   Monochoria      Monochoria vaginalis Presl.                                    Matsubai        Eleocharis acicularis L.                                       Water chestnut  Eleocharis Kuroguwai Ohwi                                      Umbrella plant  Cyperus difformis L.                                           Mizugayatsuri   Cyperus serotinus Rottboel                                     Urikawa         Sagittaria pygmaea Miq.                                        Narrowleaf      Alisma canaliculatum A. Br. et                                 waterplantain   Bouche                                                         Bulrush         Scirpus juncoides Roxburgh                                     ______________________________________                                    

However, the application of the herbicidal agents and mixed compositions according to the present invention is not limited to the above-mentioned weeds, but the application can be effected likewise also to other lowland weeds inhabiting paddy fields.

The present herbicidal agents and mixed compositions can be incorporated into any conventional formulations. As the formulations there may be mentioned, for example, a liquid agent, an emulsion, a hydrated agent, a suspension, a powdery agent, a soluble powdery agent, a granular agent, a suspended emulsion concentration, and microcapsules in a polymeric substance.

Those preparations can be prepared through well-known processes. The processes can be effected, for example, by mixing the active compounds with an extender, namely, with a liquid diluent and/or a solid diluent, and if required, with a surfactant, namely, with an emulsifier and/or dispersant and/or a foaming agent.

In using water as an extender, for example, an organic solvent can also be used together as an auxiliary solvent. As liquid diluents there may be mentioned, for example, aromatic hydrocarbons (such as xylene, toluene or alkylnaphthalene, etc.), chlorinated aromatic or chlorinated aliphatic hydrocarbons (such as chlorobenzenes, ethylene chlorides or methylene chloride, etc.), aliphatic hydrocarbons [such as cyclohexane, etc., or paraffins (for example, mineral-oil fractions, mineral or vegetable oils)], alcohols (such as butanol, glycol and ethers and esters thereof, etc.), ketones (such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, etc.), strong polar solvents ( such as dimethylformamide and dimethyl sulfoxide, etc.), and water can also be mentioned as a liquid diluent.

As solid diluents there may be mentioned ammonium salts, and natural soily minerals (such as kaolin, clay, talc, chalk, quartz, attapulgite, montmorrillonite, or diatomite etc.) and soil synthetic minerals (such as highly dispersible silicic acid, alumina, silicate, etc.). As solid carriers for granular agents there can be mentioned powdered and fractionated rocks (such as calcite, marble, pumice stone, meerschaum, dolomite, etc.), synthetic grains of organic or inorganic powders, and fine particles of organic substances (such as saw dust, coconut-shells, corn ear-stems, and tobacco stalks, etc.).

As emulsifiers and/or foaming agents there may be mentioned nonionic and anionic emulsifiers such as, for example, polyoxyethylene fatty acid esters, polyoxyethylene fatty alcohol ethers such as, for example, alkylaryl polyglycol ethers, alkyl sulfonates, alkyl sulfates, aryl sulfonates, etc., and albumin hydrolyzates.

As dispersants, for example, lignin-sulfite waste liquor and methyl cellulose are suitable.

Adhesives or stickers may also be used in the formulations in the form of a powdery agent, granular agent, jambo agent, or emulsion, and as adhesives or stickers there may be mentioned carboxy methyl cellulose, natural and synthetic polymers (such as gum arabic, polyvinyl alcohol, and polyvinyl acetate etc. for example), natural phosphatides (such as cephalins and lecithins), and synthetic phosphatides. Further, as additives there may be also used mineral and vegetable oils.

Colorants may also be used, and as such colorants there may be mentioned inorganic pigments (such as, for example, iron oxide, titanium oxide and Prussian blue), and organic dyes such as, for example, alizarin dyes, azo dyes, and metallic phthalocyanine pigments, and further trace amounts of such materials as salts of iron, manganese, boron, copper, cobalt, molybdenum and zinc.

The formulations contain generally 0.1 to 95% by weight, preferably 0.5 to 90% by weight, of the active compound (s).

In order to control weeds, the active compounds of the herbicidal agents and herbicidal compositions according to the present invention can be used as such, or in the form of formulations thereof, and the mixture can be handled in the form of formulations or in the form of tank-mixtures.

The active compounds according to the present invention can be used as mixtures with other well-known active compounds, that is, with active compounds normally used for paddy fields such as, for example, bactericides, insecticides, plant-growth regulators, plant nutritive agents, soil conditioners, safeners and any other herbicides.

To the herbidical composition according to the present invention there may be added, per part by weight of the herbicidal sulfonamides, from 1 to 200 parts by weight, preferably from 2 to 100 parts by weight, of a safener such as 1-(α,α-dimethylbenzyl)-3-p-tolylurea, for example.

The present active compounds can be used as such, as their formulations or as the use forms prepared therefrom by further dilution thereof, such as in the form of ready-to-use solutions, emulsions, suspensions, powders, wettable powders, pastes and granules.

They may be used in the customary manner, for example by watering, spraying, atomising, dusting, scattering, etc.

The present active compounds can be used either in the pre- or post-emergence period of plants. It is also possible to apply the active compounds into soil before the seeds of plants are sown.

The concentration of active compound used in the present herbicidal agents can vary within a substantially wide range. It depends essentially on the nature of the desired effect. In general, the amounts used as a herbicide are from about 0.01 to about 10 kg of active compound per hectare, preferably from about 0.1 to about 2 kg/ha.

The dosages of the present herbicidal mixed compositions may be varied within a substantially wide range, viz., from 0.1 to 5 kg/ha and preferably from 0.2 to 3 kg of active compounds per ha.

The preparation and use of the active compounds according to the present invention are illustrated by the following examples, which are only illustrative.

EXAMPLES Synthesis Examples Example 1 ##STR6##

A suspension of 1-(2-bromophenyl)-5(4H)-tetrazolinone (2 g), 4-dimethylaminopyridine (1.21 g) and N-cyclohexyl-N-ethylcarbamoyl chloride (1.89 g) in toluene (20 ml) was heated at 65°-70° C. for 8 hours. The reaction mixture, when cooled to room temperature, was washed with water and dried over anhydrous sodium sulfate. After the solvent was removed under reduced pressure, the oily residue was subjected to a flush column chromatography (hexane:ethyl acetate=5:2) to give 1˜(2-bromophenyl)-4-(N-cyclohexyl-N-ethylcarbamoyl)-5(4H)-tetrazolinone (2.1 g); m.p. 84°-86.5° C.

Further compounds obtainable by the above-mentioned reaction procedure are shown in Table 1.

                  TABLE 1                                                          ______________________________________                                          ##STR7##                                                                      Compound No.  Y       R.sup.1 R.sup.2                                          ______________________________________                                         2             H       C.sub.2 H.sub.5                                                                         ##STR8##                                        3             H       C.sub.3 H.sub.7 -n                                                                      ##STR9##                                        4             CH.sub.3                                                                               C.sub.3 H.sub.7 -n                                                                      ##STR10##                                       5             CH.sub.3                                                                               C.sub.2 H.sub.5                                                                         ##STR11##                                       ______________________________________                                    

Example 2 (Synthesis of Intermediate Compound) ##STR12##

2-bromo-phenylisocyanate (5 g) and trimethylsilylazide (4.36 g) were mixed and refluxed for sixteen hours. The excess of trimethylsilylazide was distilled off under reduced pressure, and to the resulting residue there were added 40 ml of methanol. Thereafter, the solvent was distilled under reduced pressure to give crude product that was then subjected to a flush column chromatography (hexane:ethylacetate=1:1), to obtain the desired 1-(2-bromophenyl)-5(4H)-tetrazolinone (4.1 g) having a melting point in the range of from 142.5° to 146° C.

Biotest Examples Comparative Examples (According to the Prior Art) ##STR13##

(C-1, C-2 and C-3 are similar to the compounds disclosed in the above-cited prior art documents (see, in particular, U.S. Pat. No. 4,618,365)).

Biotest Example 1

Test on herbicidal activity against lowland weeds

Formulation of Active Compounds

Carrier: 5 parts by weight of acetone

Emulsifier: 1 part by weight of benzyloxy polyglycol ether

To produce a suitable preparation of each of the active compounds, 1 part by weight of an active compound was mixed with the stated amount of carrier and with the stated amount of emulsifier, and the resulting emulsifiable concentrate was then diluted with water to the desired concentrations.

Test Procedure

Aquatic paddy soil was filled in pots (1/2,000 ares), 25×20×9 cm), and rice seedlings (variety: Nipponbare) in the 2.5 leaf stage (plant height about15 cm) were transplanted in two spots at a rate of three per hill.

Seeds of Echinochloa crus-galli P.B. var. oryzoides Ohwi, Cyperus difformis L., Scirpus juncoides Roxb., Monochoria vaginalis Presl., and annual broad-leaved weeds such as Lindernia pyxidaria L., Rotala indica Koehne, Elatine triandra Schk., Ammannia multiflora Roxb., Dopatrium junceum Hamilt. and so on, were inoculated in the pots.

The soil in the pots was maintained in wet state. Two days later, each pot was watered to a depth of about 2 to 3 cm. Five days after the transplantation of the rice seedlings, a predetermined amount of the active test compounds in the form of an emulsion, prepared in the manner described above was applied on the water-surface of each pot by means of a pipette.

After the treatment, each pot was maintained in the watered state to a depth of about 3 cm.

Three weeks after the treatment, the herbicidal effect and the degree of phytotoxicity were evaluated, wherein 100% indicating the complete death and 0% indicating no herbicidal effect.

The results are shown in Table 2.

                                      TABLE 2                                      __________________________________________________________________________     Active Compound                                                                         Dosage    Herbicidal effect (%)        Phytotoxicity                  see synthesis                                                                           of Active                        Broadleaf                                                                            (%) Rice                       Examples)                                                                               Compound (kg/ha)                                                                         Echinochloa                                                                           Cyperus                                                                             Scirpus                                                                            Monochoria                                                                            weeds (Oryza)                        __________________________________________________________________________     Invention:                                                                     1        0.3       100    100  100 100    100   0                                       0.2       100    100  90  100    90    0                              Comparative                                                                    C-1      0.3       90     100  80  90     60    15                                      0.2       80     90   70  80     50    10                             C-2      0.3       90     100  70  90     40    10                                      0.2       60     90   40  60     30    5                              C-3      0.3       80     100  70  80     40    15                                      0.2       60     80   40  50     30    10                             __________________________________________________________________________

Biotest Example 2

Test for determining herbicidal effect of the present herbicidal compositions on lowland weeds.

In a greenhouse, aquatic paddy soil was filled in pots (1/2,000 ares, 25×20×9 cm), and rice seedlings (variety: Nipponbare) in the 2.5 leaf stage with a height of 15 cm were transplanted in two spots into the pot at a rate of three per hill.

Then, the tubers of Sagittaria pygmaea Miq and small pieces of Spikerrush (Eleocharis acicularis) as well as the seeds of the following respective weeds were inoculated into the respective pots and filled with water to a height of about 2 to 3 cm above the soil surface:

Echinochloa oryzicola vasing,

Cyperus difformis L.,

Monochoria vaginalis Presl.

Broad leaved weeds such as Lindernia pyxidaria, Rotala indica Koehne, American waterwort (Elatine orientalis Makino), Ammannia multiflora Roxburgh, Dopatrium junceum Hamilton, Bulrush, Scirpus juncoides Roxburgh.

Five days after the transplantation of the rice seedlings, a predetermined amount of the active compounds in the form of an emulsion which had been prepared in the manner mentioned above, was applied on the water-surface of each pot.

After that, the water depth in each pot was maintained at about 3 cm.

Three weeks after application of the active compounds, the herbicidal effect and the degree of phytotoxicity were determined according to the following rating system, wherein 100% indicates the complete death and 0% indicates no herbicidal effect.

The results are shown in the following Table 3:

In Table 3, A, B, C and D in the herbicidal compositions under test represent the following active compounds, respectively:

A: Methyl 2-[3-(4,6-dimethoxypyrimidin-2-yl)-ureidosulfonylmethyl]benzoate,

B: Ethyl 5-[3-(4,6-dimethoxypyrimidin-2-yl)-ureidosulfonyl]-1-methylpyrazole-4-carboxylate,

C: N-(2-chloroimidazolo[1,2-a]pyridin-3-yl-sulfonyl)-N'-(4,6-dimethoxy-2-pyrimidyl)urea,

D: Methyl 2-[4,6-dimethoxy-2-pyrimidinyl)oxy]-6-[1-(methoxyimino)-ethyl]-benzoate.

                                      TABLE 3                                      __________________________________________________________________________           Dosage of Herbicidal Effect (%)                   Phyto-                 Active                                                                               Active Compounds                                                                         Echi-     Mono-                                                                              Broadleaf      Spikerrush toxicity (%)           Compounds                                                                            (kg/ha)   nochloa                                                                             Cyperus                                                                             choria                                                                             weeds Scirpus                                                                            Sagittaria                                                                          (Eleocharis                                                                               Rice                   __________________________________________________________________________                                                             (Oryza)                1 + A 0.10 + 0.075                                                                             100  100  100 100   100 100  --         0                      1 + B 0.10 + 0.021                                                                             100  100  100 100   100 100  --         0                      1 + C 0.10 + 0.09                                                                              100  100  100 100   100 100  --         0                      1 + D (*1)                                                                           0.10 + 0.03                                                                              100  --   --  --    --  --   --         0                      1     0.10      80   100   80  90    70  0   --         0                      1 (*2)                                                                               0.10      80   --   --  --    --  --   --         0                      A     0.075     40   100  100 100   100 100  --         0                      B     0.021     50   100  100 100   100 100  --         0                      C     0.09      50   100  100 100   100 100  --         0                      D (*3)                                                                               0.03      80   --   --  --    --  --   --         0                      __________________________________________________________________________

In Table 3, the composition indicated by (*1) controlled the emergence of Barnyard grass (Echinochloa) for a period of forty-seven days, while the compound No. 1 indicated by (*2) controlled said emergence for a period of forty-five days, and the compound D (*3) controlled said emergence for a period of twenty days.

Formulation Example 1

Water was added to a mixture consisting of 1 part by weight of the above-mentioned active compound No. 1, 0.25 parts by weight of the above-mentioned active compound A, 30 parts by weight of bentonite, 66.75 parts by weight of talc, and 2 parts by weight of lignin sulfonate, followed by an intimate kneading, granulating and drying to obtain granules.

It will be understood that the specification and examples are illustrative but not limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art. 

We claim:
 1. A tetrazolinone of the formula ##STR14## wherein Y is hydrogen, bromine or methylR¹ is ethyl or n-propyl, and R² is cyclopentyl or cyclohexyl,with the proviso that the total number of carbon atoms in R¹ and R² is 7 or
 8. 2. A compound according to claim 1, whereinY is hydrogen or methyl.
 3. A compound according to claim 1, wherein such compound is 1-(2-bromophenyl)-4-(N-cyclohexyl-N-ethylcarbamoyl)-5(4H)-tetrazolinone of the formula ##STR15##
 4. A compound according to claim 1, wherein such compound is 1-(2-bromo-6-methylphenyl)-4-(N-cyclopentyl-N-n-propyl-carbamoyl)-5(4H)-tetrazolinone of the formula ##STR16##
 5. A herbicidal composition comprising a herbicidally effective amount of a tetrazolinone according to claim 1 and a diluent.
 6. A method of combating unwanted vegetation which comprises applying to such vegetation or to a locus from which it is desired to exclude such vegetation a herbicidally effective amount of a tetratrazoline according to claim
 1. 7. The method according to claim 6, wherein such compound is 1-(2-bromophenyl)-4-(N-cyclohexyl-N-ethylcarbomoyl)-5(4H) tetrazolinone or 1-(2-bromo -6-methylpheenyl)-4-( N-cyclopentyl-N-n-propyl-carbamoyl)-5(4H)-tetrazolinone. 